The present invention relates to a method and a device for manufacturing a tool and a tool made by the method.
It is previously known through for example WO 98/28455 to press material powder, such as tungsten carbide (WC) together with cobalt (Co), between a punch and a die, and subsequently to sinter the material such that the binder metal is melted and binds the carbides to form tool material for chip removing machining. The known technique brings about a plurality of drawbacks. The powder [give] gives off dust and the formed green body (pressed but not sintered material) will not endure handling to any degree. Furthermore the chip flutes must be ground and the method requires time and energy. The problems have partly been solved by the injection molding of hard metal mixed in a carrier such as indicated in U.S. Pat. No. 5,947,660. The method of injection moulding brings a high degree of freedom concerning geometry but brings costly investments in moulds.
Through U.S. Pat. No. 4,779,440 a tool is previously known for forming a blank for a helix drill. An extruded drill blank having chip flutes of constant pitch along the circumference of the blank is obtained by heating a hard metal powder to extrusion temperature, pressing the heated powder blank under high energy consumption through a space defined by a mandrel and a nozzle while rotating the blank. The blank is guided during the extrusion past a helical ridge provided at the inside of the nozzle, to shape helical chip flutes along the blank as the blank rotates. A drawback of the known technique is that the chip flutes are obtained along the entire length of the blank.
One object of the present invention is to provide a method, a device and a tool, whereby the drawbacks of the known technique are eliminated.
Another object of the present invention is to provide a method and a device whereby the lengths of the chip flutes can be determined.
These and other objects have been achieved by a method and apparatus for manufacturing a tool as well as a tool made by the method.
The method of manufacturing a rotary tool for chip removing machining comprises the steps of:
A. providing a mixture of a hard metal powder and a carrier;
B. heating the mixture;
C. extruding the heated mixture in a feed direction through a die which forms the mixture with a cylindrical outer surface;
D. conducting the mixture past a flute-forming structure which forms a chip flute along a first section of the outer surface;
E. displacing the flute-forming structure laterally away from the outer surface during step C for terminating the chip flute formation along a second section of the outer surface which defines a shank portion;
F. allowing the mixture to solidify and form a blank; and
G. sintering the blank.
The apparatus is adapted to be mounted to an extrusion machine for shaping a mixture received from the extrusion machine into a rotary tool for chip forming machining. The apparatus comprises a housing which is adapted to be mounted to an extrusion machine and forms a through-passage for conducting the mixture in a feed direction. The through-passage defines a center axis. A nozzle is provided which forms a restriction in the passage. A die is disposed downstream of the nozzle and includes a through-hole. At least one jaw is situated adjacent a downstream end of the die and is movable toward the axis to an inner position in engagement with the mixture received from the die for applying a shape thereto. The die is movable away from the axis to an outer position to avoid applying the shape thereto.
The invention also pertains to a rotary tool made by the above-described method.